Surface Modification Using Amino Acid to Induce Low-Oxidation-State Co Centers with Proton-Accumulation Effect for Electrocatalytic Hydrogen Evolution
Yingying Gao, Sheng Qian, Bo Peng, Junhua Wang, Huaiguo Xue, Tengfei Jiang, Jingqi Tian
Abstract
The electrocatalytic hydrogen evolution reaction (HER) requires high-performance catalysts, wherein both the valence state and the reaction microenvironment of the catalytic metal centers play a crucial role in the electrocatalytic activity. Herein, we demonstrate a surface modification strategy using a library of amino acid molecules to noncovalently link on cobalt phosphide (AA-CoP). We hypothesize that in amino acid molecules, the electron-donating functional group on the side chain tailors the valence state of Co centers, and the proton donor/acceptor groups can serve as a proton accumulator between the bulk electrolyte and catalyst surface via a hydrogen-bonding network, inducing a local proton-enriched environment on the electron-rich Co centers for electrocatalytic HER. We further propose a descriptor (φ), expressed as Q N × N H × V –1, to describe the geometric and electronic features of the amino acid molecules, which intrinsically quantifies their effect on metal centers for HER. In the volcanic relationship between this descriptor and HER activity based on the evaluation of 7 kinds of amino acid, asparagine-modified CoP (Asn-CoP) locates nearest to the summit, with only 112 mV to achieve 100 mA cm –2, which can be attributed to the sufficiently negative Co sites that are favorable to form the Co–H intermediate and to the hydrogen-bonding network-based microenvironment that supplies protons for HER.